Copying-pad



.' UNITED STATES PATENT OFFICE.

NAT B. BROWNE,

COMPANY, OF

OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO THE HYPERGRAPH LOS ANGELES, CALIFORNIA, A CORPORATION OF CALIFORNIA.

COPYING-PAD.

No Drawing.

To all who 11bit may concern:

Be it known that I. NAT B. BnowNn, a citizen of the United States, residing at Los Angeles. in the county of Los Angeles and State of (alifornizu have invented new and useful Improvements in Copying-Pads, of which the following is a specification.

My invention relates to a composition for copying pads and has for its object a copying pad inexpensive of manufacture and capable of making copies of printed or writ- 'ten matter, made by means of any commercial copying ink of any color.

My invention consists in the composition of matter hereinafter described and claimed.

The following ingredients are used, the parts being taken by weight: magnesium silicate 200 parts, calcium carbonate 150 parts, magnesium sulfate 10 parts, acacia gum 3?; parts, gum tragacanth 3}, parts, dextrin parts, glycerin 130 parts.

The ingredients are compounded as follows: In a suitable receptacle the glycerin is placed and heated and thedextrin, acacia gum, gum tragacanth and magnesium sulfate are added and the temperature raised to about 150 1*. being careful not to bring the mixture to a boil in' order to prevent destructive reactions. The mixture is thoroughly stirred until a homogeneous mass is formed. The magnesium silicate and calcium carbonate are now incorporated and the mixture agitated until the ingredients form a homogeneous mass. It may be mentioned here that the magnesium silicate and calcium carbonate used are in the form of an extremely fine powder. The mass is now spread upon a table in a thin layer and allowed to undergo an aging process for a few days. It has the consistency and color of white putty and is of a granular texture. It is now ready for use in the copying pad which may consist of a shallow frame with a flat bottom and side walls of small dimensions. The composition is placed in the frame and compacted by suitable means, such as a roller or mallet. By rubbing a moistened sponge over the surface a flat polished surface is produced thereon.

In making a copy from a sheet printed or written with copying ink the sheet to be copied is placed with the printed face downward on the copying pad and pressed firmly against the pad by any suitable means. The sheet is now removed from the pad, which latter will now have an imprint of the print- Speeification of Letters Patent.

Patented Jan. 4. 1921.

Application filed March 30, 1920. Serial No. 370,034.

ed or written matter on the sheet. A blank sheet of paper is now placed on the copying pad and suitable pressure exerted thereon. ()n removing the sheet of paper a copy of the printed matter will appear on the same. Many copies may be made from the same imprint. or imprints may be made from the first few copies taken from the copying pad.

To restore the copying pad for the next operation it is merely necessary to use a wet sponge to wipe off the imprint.

While I prefer to use a mixture of dextrin, acacia gum and gum tragacanth, only one of these or any two of them may be used, provided the same quantity is employed. The magnesium silicate produces an extremely line granular texture of the composition and the calcium carbonate is used to give it the proper density. The magnesium sulfate is a fixative soluble in glycerin and prevents the ink from running on the pad. Furthermore, magnesium sulfate will not precipitate the adhesives mentioned, namely, acacia gum. gum tragacanth and dextrin, from the solution. It should be noted that said adhesives are all soluble in glycerin.

It will be understood that various changes may be made by those skilled in the art without departing from the spirit of my invention as claimed and that the proportions of the ingredients may be varied within wide limits. The best results, however, are obtained by adhering closely thereto.

I claim:

1. A composition for a copying pad for nesium sulfate 10 warts acacia um 3?, )arts gum t 'agacanth 3?; parts, dextrin 3?, parts, and glycerin 130 parts.

In testimony whereof I have signed my name to this specification.

NAT B. BROWNE. 

